Suspension assemblies are used in oilfield operations to hold and support a work string, (e.g., a tubular such as drill pipe) in a vertical position above the rig floor to enable the addition to or removal of a joint or section of the work string from the upper end thereof. These assemblies may include insert bowls, bushings, or spiders, each comprising a bowl with a central bore through which the work string extends. The central bore of the bowl is defined by an inner surface. The inner surface is usually tapered so that the diameter of the upper section of the central bore is greater than the diameter of the lower section of the central bore. An example of a bowl is described in U.S. Pat. No. 4,332,062 and in U.S. Pat. No. 5,351,767.
A slip assembly may also form part of the suspension assembly. The slip assembly may have multiple slips with an inner surface designed to grip the work string when the slip assembly is secured to a section of the outer wall of the work string. The outer surface of the slips have a tapered contour that is designed to mate with and engage the corresponding tapered inner surface of the bowl when the slip assembly (with secured work string) is situated within the bore of the bowl. An example of a slip assembly is described in U.S. Pat. No. 6,471,439 and in U.S. patent application Publication No. 2002/0061224.
A rotary table may also be included as part of the suspension assembly. The rotary table is mounted to the floor of the rig. The rotary table has a contoured bore that is designed to accommodate an insert bowl, bushing, or spider. An example of a rotary table is described in U.S. Pat. No. 6,471,439.
To suspend and hold the work string using the suspension assembly, the rotation of the work string is stopped. The slip assembly is positioned around a section of the outer wall of the work string. The slip assembly (together with the attached work string) is lowered into the bore of the bowl where the slip assembly is wedged therein as the tapered outer surface of the slips engage the tapered inner surface of the bowl. The wedging of the slip assembly in the bowl causes the slips to further exert pressure against the work string to grip and hold the work string in a vertical, suspended position above the rig floor so additional joints or sections can be added to or removed from the work string.
Repeated use of the suspension assembly may cause wear and fatigue to the components, particularly the bowl and slips which are prone to wear as a result of the metal-to-metal abrasive contact between them. In addition, the work string may contact the bowl on occasion during drilling operations and cause further wear to the bowl, namely to the inner surface area. The section of the inner surface of the bowl at the bottom of the taper (referred to as the throat) is particularly vulnerable and subject to degradation because this is where the greatest load is placed and where the work string tends to make contact.
FIG. 1 shows what can happen to a bowl that is worn beyond design specifications for desired use. Bowl 11 exhibits wear 28 to inner surface 16, namely to lower section 18 of inner surface 16.
Because of wear 28 to inner surface 16 of bowl 11, bowl 11 does not adequately support slips 13, particularly in area 34 where outer surface 33 of slips 13 no longer contacts or engages inner surface 16 of bowl 11. This loss of contact and support in area 34 of inner surface 16 of bowl 11 means that the gripping force applied to work string 14 by slips 13 is no longer evenly distributed but instead is concentrated in area 29 of work string 14. The concentration of force in area 29 may cause bottlenecking of work string 14 at area 30 as well as crushing of or excessive slip cuts in work string 14.
Due to the spreading of lower section 31 of slips 13 and the loss of contact between lower section 31 of slips 13 and work string 14 at area 32, the gripping area of slips 13 is reduced, which may result in slips 13 failing to hold and support work string 14.
Insert bowls, bushings, and spiders are manufactured in accordance with applicable standards set by the American Petroleum Institute (API). For example, API specifications require a new number 3 bowl to have a throat diameter (diameter of area at the bottom of the taper) of 10⅛ inches. Generally, the industry practice is to replace the bowl when the maximum wear as measured at the throat of the bowl reaches 10⅝ inches to 10⅞ inches.
To determine if the dimensions of the throat of the bowl exceed 10⅝ inches, it is necessary to measure the diameter of the throat of the bowl using mechanical calipers. Such measurement by hand using a caliper is difficult because of the tapered contour of the inner surface of the bowl, which may lead to an incorrect measurement.
If the bowl is positioned in a rotary table, the bowl must first be removed before a measurement can be taken. Removing the bowl from the rotary table is a time consuming and difficult procedure. Any work string extending through the bowl will need to be dismantled and removed if the bowl is of a single-piece design and does not have separate detachable components.
Even if the bowl is a split bowl having two detachable components, maneuvering the bowl components from the rotary table to a level surface and reassembling them for measurement is troublesome as the components are awkwardly shaped and heavy making them difficult to manipulate. Moreover, properly aligning the bowl components in their operational position outside of the rotary table is problematic. An incorrect alignment may lead to an error in the measurement of the throat diameter.
U.S. Pat. No. 6,354,380 describes an insert bowl for use with a wireline. The insert bowl has a vertical groove formed in the inner surface of the bowl. The vertical groove positions and contains the wireline that is run down through the bore of the insert bowl. The vertical groove does not function as a wear indicator means to visually inspect wear to the insert bowl.
The foregoing disadvantages and problems of detecting wear to an insert bowl, bushing, or spider are overcome by the apparatus and method of the present invention wherein a wear indicator means formed in the inner surface of the bowl enables visual detection of wear so that the bowl can be replaced before damage is caused to the work string.